Kernel driver `pca9540.o'
=========================

Status: Complete but untested

Supported chips:
  * Philips PCA9540
    Prefix: 'pca9540'
    Addresses scanned: I2C 0x70
    Datasheet: Publicly available at the Philips Semiconductors website
               http://www.semiconductors.philips.com/pip/PCA9540.html

Authors: Jean Delvare <khali@linux-fr.org>


Module Parameters
-----------------

* force: short array (min = 1, max = 48)
  List of adapter,address pairs to boldly assume to be present
* force_pca9540: short array (min = 1, max = 48)
  List of adapter,address pairs which are unquestionably assumed to
  contain a `pca9540' chip
* ignore: short array (min = 1, max = 48)
  List of adapter,address pairs not to scan
* ignore_range: short array (min = 1, max = 48)
  List of adapter,start-addr,end-addr triples not to scan
* probe: short array (min = 1, max = 48)
  List of adapter,address pairs to scan additionally
* probe_range: short array (min = 1, max = 48)
  List of adapter,start-addr,end-addr triples to scan additionally

Note that the force and force_pca9540 parameters are equivalent here.


Description (from the Philips web site)
---------------------------------------

The PCA9540 is a 1-of-2 bi-directional translating multiplexer, controlled
via the I2C bus. The SCL/SDA upstream pair fans out to two SCL/SDA downstream
pairs, or channels. Only one SCL/SDA channel is selected at a time,
determined by the contents of the programmable control register.


Accessing the PCA9540
---------------------

The PCA9540 is almost impossible to detect. We are lucky that no other
known chip lives at address 0x70.

Beware that the PCA9540 has a single internal register. It does work with
READ BYTE and WRITE BYTE commands, contrary to regular chips which use
READ BYTE DATA and WRITE BYTE DATA. Using i2cdump on the PCA9540 will
actually *write* to it and leave its internal register to value 0x07 (i.e.
no downstream channel selected).


/proc Interface
---------------

There is a single read/write file, named "channel".

 0 = no downstream channel selected
 1 = first downstream channel selected
 2 = second downstream channel selected


Chip Features
-------------

Chip `pca9540'
          LABEL     LABEL CLASS   COMPUTE CLASS ACCESS MAGNITUDE
        channel            NONE            NONE     RW     0

          LABEL                   FEATURE SYMBOL     SYSCTL FILE:OFFSET
        channel          SENSORS_PCA9540_CHANNEL         channel:1
